Roast the Squash: Heat oven to 400°F. Cube 2 cups of your favorite winter squash (I like honeynut or butternut), toss with a tablespoon olive oil and season with salt and pepper. Roast on a baking sheet until tender and caramelized, about 20 minutes. Reduce oven temperature to 350°F
Toast the Bread: Tear 6 bolillos into big chunks and spread on a separate large baking sheet. Toast in a 375°F oven until crispy on the outside but still chewy on the inside, about 10-15 minutes. Leave the oven on.
Sweat the Veggies: In a large skillet over medium heat, melt the 2 sticks of butter. Add 10 ounces pearl onions and 3 stalks of diced celery, season with kosher salt and black pepper, and cook gently until onions are translucent and just starting to brown. Stir in 3 cloves minced garlic and cook another minute.
Toast the Ancho Strips: Slice 3 dried ancho chiles into thin strips and toast in a medium dry skillet over medium-high heat for a minute or two, until fragrant and pliable. Remove from the pan immediately to prevent burning.
Mix the Stuffing: In a large mixing bowl, combine toasted bread, sautéed veggies, roasted squash, 1/4 cup sliced fresh sage leaves, 1 cup pepitas, toasted ancho strips, and 1/2 cup dried cranberries. Toss gently so every bread cube gets coated in flavor. Taste and adjust salt and pepper as needed.
Add Stock: Whisk together 2 large eggs and 4 cups vegetable stock or broth until combined. Pour over the stuffing mixture. Stir until everything is evenly moistened.
Generously butter a 9 x 13-inch baking dish. Spoon half of the stuffing into the dish. Spoon 5-6 generous spoonfuls of cilantro pesto over the top and spread into an even layer. Spoon the remaining stuffing on top and spoon another 3-4 generous spoonfuls of pesto on top.
Bake: Cover with aluminum foil, and bake at 375°F for 25 minutes. Remove foil and bake another 15–20 minutes until the top is golden brown and crisp on top.
Serve: Finish with extra pepitas, a sprinkle of fresh sage, and a generous drizzle of cilantro pesto over the top. Serve warm. Store leftovers in an airtight container and refrigerate for up to 5 days.